I haven't watched this yet, got it on the Sky+ though. I started martial arts when I was 6. Karate, tae kwon do, gung fu, boxing, jeet kune do, muay thai... I was in competitions/tournaments by the time I was 8 and invited to fight for GB when I was 10.
There's nothing up with a bit of keep fit, disciplined training and tournaments so long as the kids enjoy it imho. They're a whole lot less likely to turn into chav scum than some dope brought up in a house full of booze-heads (or worse) who don't care if their child even goes to school, let alone gets a hobby and keeps fit. Meh.